±10 V quick question

Thread Starter

Tony Elliott

Joined May 8, 2015
144
Here is the instructions, the bit is on the left hand top corner. Its creating a panning circuit using Voltage Controlled Amplifiers. I also need to work out how to how to make a wave 180 degrees out of phase.

vca.JPG
 

AnalogKid

Joined Aug 1, 2013
8,251
Based on that, the LFO output is a 10 V peak-to peak sinewve centered about GND. Thus the two peaks are +5V and -5V with respect to GND. The required signal is 0V to 5 V, so that is a 2:1 attenuation. The required output centerpoint is +2.5V, so that is a 2.5V addition or offset. So the total conversion circuit is a gain of 0.5 and an offset of +2.5V.

The two circuits on the left indicate creating the offset by combining a DC voltage with the LFO signal. Another approach is to bias the input to the amplifier at 2.5V and AC couple the LFO signal. This prevents any residual DC in the LFO signal from winding up in the output.

Why are you amplitude-modulating audio with a low frequency sinewave?

ak
 

Thread Starter

Tony Elliott

Joined May 8, 2015
144
Based on that, the LFO output is a 10 V peak-to peak sinewve centered about GND. Thus the two peaks are +5V and -5V with respect to GND. The required signal is 0V to 5 V, so that is a 2:1 attenuation. The required output centerpoint is +2.5V, so that is a 2.5V addition or offset. So the total conversion circuit is a gain of 0.5 and an offset of +2.5V.

The two circuits on the left indicate creating the offset by combining a DC voltage with the LFO signal. Another approach is to bias the input to the amplifier at 2.5V and AC couple the LFO signal. This prevents any residual DC in the LFO signal from winding up in the output.

Why are you amplitude-modulating audio with a low frequency sinewave?

ak
I am creating a voltage controlled panning circuit to experiment with space.
 

Lestraveled

Joined May 19, 2014
1,946
Have you been tasked to build this circuit and to work out the details? Is so, do you know how to determine the resistor values for the op-amps?
 

#12

Joined Nov 30, 2010
18,167
I can visualize the result.:) A stereo signal would seem to move back and forth across the room as one speaker goes from full output to zero and back, while the other speaker goes from zero output to full and back to zero. Bit of a mind-melt, but sometimes that's what you want to do with the art.

For those to whom this is not obvious, I hope I explained it.
In addition, I recommend people withhold judgement about the motives. We do lots of circuits here without deciding if the Thread Poster has good reasons to do them.;)
 

AnalogKid

Joined Aug 1, 2013
8,251
The resistor values are already calculated, this is the VCA I need to use parts of this schematic.
I know this part. It is a classic from audio console designs in the 80's. Getting the control voltage just right usually takes a couple of trimpots, but it will do what you want. Any other questions?

ak
 
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